1. Test serums from patients with non-A, non-B hepatitis for presence of immune complexes by RAJI cell assay and compare with patients with other forms of viral hepatitis and with controls without hepatitis. 2. Isolate complexes from non-A, non-B patients with high level activity by RAJI assay; dissociate complex and test derived "antigen" and "antibody" for non-A, non-B specificity by solid phase radioimmunoassay.